In the past 7 days I have updated to Xcode 5.1 seven times!
Yesterday I dragged Xcode to the trash and emptied the trash in an attempt to make it stick, this morning I got a popup saying that Xcode had been auto updated (should it even do that?) EDIT it is a preference setting!) but there is still an update showing Xcode 5.1 as being available.
I have now dragged Xcode to the trash, emptied the trash, rebooted and fixed permissions. Noting the previous thread about repeated updates I have enabled the App store debug menu and cleared cookies and reset the application. In desperation I even shutdown my NAS which has the old version of Xcode on it (I invoke Time Machine manually)
I am trying to resolve an issue with my ISP and this is not helping. Before I install Xcode for the 8th time, is there anything else I can do to convince the App store that it has indeed updated Xcode?
EDIT: Despite the above preparations, I updated Xcode just now and another update is already showing as being available!
EDIT: I may have solved the problem. Another application needed updating and then also exhibited the repeated download issue. Reading around I discovered comments about Spotlight and App Store issues. The Spotlight fixes didn't seem to do anything for me but I read a comment that deleting some dubious looking files in "/Library/Application Support/App Store" seemed to do the trick. I moved these 3 files to a temporary directory and rebooted. At last! The problem seems to have been fixed. 2 of the files were recreated, the 3rd (utd.plist) wasn't. I will leave it for a few days before declaring success.